1. Field of the Invention
The present invention relates to a control apparatus and method for a motor vehicle having an engine and a continuously variable transmission drivingly connected to the engine.
2. Description of the Prior Art
In motor vehicles having an engine and an ordinary transmission drivingly connected to the engine, if a reduction ratio is selected, the engine is operated at a single rpm for a vehicle speed. With the conventional control apparatus, therefore, the engine is allowed to operate at any revolution speed over the whole operating range for a reduction ratio within the transmission and a driver is allowed to set an operating state of a fuel supply device, for example, a throttle opening degree of a carburetor, to any desired state as he or she desires under any driving state. It is the common practice to use almost all of the possible combinations of engine revolution speed and throttle opening. In the case of engines commonly used in motor vehicles, with various combinations of engine revolution speed and throttle opening, an engine is able to produce the same horsepower output, but fuel consumption rate differs for different combinations. Since according to the conventional control apparatus various combinations of engine revolution speed and operating state of the fuel supply device, for example, a throttle opening degree or an engine intake manifold vacuum corresponding to the throttle opening degree or a fuel supply amount, are used, the engine is operated even in an operating region wherein the fuel consumption rate is bad. This causes an increase in fuel consumption rate, leading to poor energy effeciency.